It is not clear how long it takes for lung cancer to form, but usually it takes several years or decades, and the exact time varies from person to person. Lung cancer is a malignant tumor of the respiratory system, and the formation of tumor is a slow process. In addition to certain genetic factors, the formation of lung cancer is also related to the patient’s lifestyle, such as smoking, occupational environment, atmospheric pollution, and the patient’s own immunity. If there is a definite family history of tumor inheritance, the patient’s susceptibility is relatively high and regular tumor screening is recommended. In addition, those who have a history of smoking should also be screened regularly. Patients with lung cancer do not have obvious symptoms at the beginning, so it is not easy to be detected. Only when the cancer occurs for a certain period of time, symptoms will appear, which are usually detected by conducting examinations. In addition, common symptoms of lung cancer include cough and blood in sputum, etc. If corresponding symptoms occur, you should go to the oncology department of the hospital for examination in time.